1. Field of the Invention
The present invention relates to transmitting analog and digital television signals over a wireless link.
2. Prior Art
Coaxial cable has a large signal bandwidth enabling transmission of many channels, which allows cable television service providers to offer a broad range of programming to subscribers. Many cable television systems offer analog TV channels and digital TV channels. Analog channels are occupied with programming of established over the air stations, programming supported by advertising, or programming desired by most subscribers. Some premium services are offered on analog channels that use scrambling or blocking to unauthorized users. Digital channels offer better utilization of the frequency spectrum, potentially higher quality images, and robust security against unauthorized reception. Many premium services are transmitted on digital channels. Digital programming is commonly transmitted using Motion Picture Experts Group (MPEG) encoding and formatting. The bit rate of an MPEG encoded video signal may be approximately 1.5 Mbits/S to 15 Mbits/S and generally includes a digital audio signal. An in-home receiving system must support reception of both analog and digital channels from the cable system.
Wiring must be installed in homes and each television must be connected to the cable to receive the cable system signal. Installing wiring in an existing structure when adding new television receivers or moving their location presents a cost burden and inconvenience to the user.
FIG. 1 shows a typical wiring configuration of a home wired with coaxial cable. The cable signal enters the home at a point of entry (POE). A splitter divides the signal power and drives coaxial cables run to each room. A set top box may be used to convert the signal, or the cable may be connected directly to a cable ready television receiver. A coaxial cable must be run to each room where a television is used.
U.S. Pat. No. 5,936,660 by Gurantz entitled “Digital Video Converter Box for Subscriber/Home with Multiple Television Sets”, incorporated herein by reference, discloses a distribution technique for digital video programming to multiple television receivers. This reference includes a suggestion of a wireless RF link to transmit the video program to the television. This reference does not address the need to distribute both analog and digital video programming in the home. This reference discloses the use of a single chassis containing conditional access for all televisions and eliminates set-top converter boxes at each television. Authorization of each television signal is done at the central distribution point before transmission to the television set. The focus of the reference is primarily for distribution over cable and does not address the need for secure transmission over the wireless RF link.
It is desirable to overcome the cable wiring difficulty to enable the analog and digital programming available from the cable service to be sent to any television receiver in the home.